Method and apparatus for controlling the degree of tightness of bolts or nuts driven by an impact wrench



July 20, 1965 K. G. KARDEN 3,195,655

METHOD AND APPARATUS FOR CONTROLLING THE DEGREE OF TIGHTNESS OF BOLTSORNUTS DRIVEN BY AN IMPACT WRENCH Filed Dec. 2. 1960 2 Sheets-Sheet l July20, 1965 K. G. KARDEN 3,195,655

METHOD AND APPARATUS FOR CONTROLLING THE DEGREE OF TIGHTNESS OF BOLTS 0RNUTS DRIVEN BY AN IMPACT WRENCH Filed Dec. 2, 1960 2 Sheets-Sheet 2 so51 L 59 58 ATTORNEY United States Patent O snaasss MlETl-LGD ANDAPPARATUS QGl lTRfiLLlNG THE DEGREE (ll 'lTilGlld'lNllfid @F lliIlLTg @RNUTS DRlV'EN AN IME ACT WRENQH Karl Gilsia Ha den, Nacho, Sweden,assignor to Atlas Copeo ole-g, Nacho, Sweden, a corporation of wedenFiled Bee. 2, 1%5, Ser. No. 73,316 17 Claims. (ill. 173 l) Thisinvention relates to a method and an apparatus for controlling thedegree or" tightness of a series of bolts or nuts driven by an impactwrench. Such control is important in many technical applications, forexample in the assembly of structural building elements, in order togive the joints the intended maximum of strength.

One object of the invention is to provide a simple and eflicient controlof the maximum torque transmitted to the work by an impact wrench sothat a series of bolts or nuts can be tightened with suflicient accuracyto substantially the same degree or tightness.

Another object of the invention is to provide a torque control of theforegoing character which avoids constructional complication of theimpact wrench proper by performing said control externally of the impactwrench.

A further object of the invention is to provide a torque control of theforegoing character which is applicable together with fluid operatedimpact wrenches irrespective of type.

For the above and other purposes the invention contemplates a method andapparatus by which the total quantity or" pressure fluid delivered tooperate the impact wrench is controlled and the fluid supply to theimpact wrench is interrupted upon reaching a delivery of a predeterminedfluid quantity.

The quantity of pressure fluid used up by an impact wrench duringoperation depends normally upon the number of revolutions performed bythe wrench motor. If the supply pressure and the total fluid quantitydelivered to the Wrench are kept constant the wrench motor is bound tooperate a fixed number of revolutions. When a series of similar bolts ornuts are to be tightened and applied under similar conditions, as oftenis the case in practice, the tightening of each nut will require thesame number of running down and impacting revolutions, i.e. will requiresubstantially an equal air quantity to be delivered to the wrench.Accordingly, the invention proposes to deliver for each tighteningoperation of the wrench a predetermined constant quantity of pressurefluid to the impact wrench, said quantity being chosen so that each boltor nut will be set with the same required degree of tightness. Thequantity of pressure fluid required for each type of work will easily befound in the initial production stage by controlling the torque valueattained, for example with the help of a conventional torque measuringspanner wrench.

The above and other objects of the invention will become obvious fromthe following description and from the accompanying drawings in whichthree embodiments of the invention are illustrated by way of example. Itshould be understood that these embodiments are only illustrative of theinvention and that various modifications may be made within the scope ofthe claims without departing from the scope of the invention.

In the drawings, wherein like parts are designated by like referencecharacters throghout the several views,

FIG. 1 shows a diagrammatic view partly in longitudinal section of anapparatus representing one embodiment of the invention;

PEG. 2 shows a diagrammatic view in longitudinal section of a modifiedform of the pressure fluid controlling device included in the apparatusaccording to FIG. 1;

ice

FIG. 3 shows an enlarged longitudinal section of the valved portion ofthe piston shown in FIG. 2; and

FIG. 4 is a diagrammatic view partly in longitudinal section of anapparatus representing a third embodiment of the invention.

In the drawings l designates a fluid operated impact wrench ofconventional design, having a suitable impact clutch mechanism, drivenfor example by a compressed air motor of the rotary sliding vane type.The impact wrench may be carried out according to Swedish Patent Number126,061 or in other way. The illustrated impact wrench 1 has a handle 3to which is coupled an air conduit 2 supplying compressed air to operatethe wrench motor. The air supply is controlled by a trigger operatedthrottle valve 4 arranged in the tool handle 3. The impact wrench ll hasthe usual tool socket 5 for cooperation with the work, such as a bolt ornut s to be tightened. The conduit 2 receives air from a compressed airsource 7 with great enough a capacity to deliver compressed air ofsubstantially constant pressure to the impact Wrench 3 when the latteris operating.

According to the invention and referring to FIG. 1 there is arranged adevice generally designated 8 between the compressed air source 7 andthe impact wrench l for controlling the pressure fluid quantitydelivered for the operation of the impact wrench l. The device 8consists of a cylinder 9, one end of which is connected by a conduitltil to the compressed air source 7. The other end of the cylinder 9 isconnected to the conduit 2 leading to the impact wrench ll. Within thecylinder 9 is reciprocably arranged a differential piston 11 dividingthe cylinder into a pressure chamber 13 and a delivery chamber 19. Thepiston 13 has a threaded stem 12., which projects int-o and to which isthreaded a hollow member 13 projecting through one end wall 9a of thecylinder 9. Inside of the cylinder 9 the hollow member 13 forms a stopflange 14 cooperating with the end wall 9a through which said member 13projects. A lever 15 is fixedly secured to the free end of the hollowmember 13. Turning of the threaded hollow member 13 by the lever 15brings about a displacement of the stop flange i l with respect to thepiston ll so that the upper end position of the piston 11 in thecylinder 9 is changed. A sealing ring 15, carried by the piston 11 andanother sealing ring 17 in the end wall 9a of the cylinder 9 around thehollow member 13 seal the pressure chamber 18 and the delivery chamber19.

The chambers 18 and 19 of the cylinder are in com munication with eachother through a restricted bleed passage 29 which extends axiallythrough the piston 11 inside of an annular sealing pad 21. The sealingpad 21 is coaxial with the piston ll and in the dotted line or lowerposition of the piston in FIG. 1 contacts an annular rib 22 or valveseat inside of the cylinder on the end wall 9b thereof whereby theportion of the delivery chamber 19 which is radially outside of the rib22 may be separated from the conduit 2. to th impact wrench ll. Nearsaid end wall 912 of the cylinder there is a communication through aconduit 23 and an adjustable needle valve 24 between the deliverychamber 19 and the pressure chamber 18. By adjusting the bleed openingof the needle valve 24 an adjustable additional quantity of live air maypass from the pressure chamber 8 to the delivery chamber 19 during thedownward stroke of the piston until the annular sealing pad 21 contactsthe rib 2.2 and cuts oil the communication between the conduits 23 and2.

The apparatus according to FIG. 1 operates in the following manner: Inthe illustrated full line position of the piston lit and assuming theneedle valve 24 to be closed, the operator grasps the impact wrench bythe handle 3 and places the socket 5' of the wrench over the nut or bolt6, whereupon he presses the trigger to open the throttle valve 4. Suchactuation brings the delivery chamber 19 and the conduit 2 intocommunication with the motor of the wrench 1 and starts the motor whichby consuming air creates a pressure drop in said conduit 2 and thechamber 19 with respect to the pressure chamber 18 of the cylinder 9 Thevalue of this pressure drop is defined by the difference-in effectivepressure areas on the opposite sides of the differential piston 11. Assoon as the pressure in the delivery chamber 19 falls just below thevalue necessary for balancing the piston 11, the piston begins to movedownward and feeds the fluid volume trapped in front of it to operatethe wrench ll. Upon reaching the end of its stroke the piston 11 isarrested in its bottom position in cylinder 9 interrupting furtherdelivery of sufficient live air to operate the wrench 1 so that thetightening of the nut 6 ceases. The pressure drop causes anuninterrupted leakage of a small amount of live air through therestricted bleed passage 2% of the piston 11 into the chamber 1)- Thisleakage is too small to build up pressure in the delivery chamber 19 aslong as the throttle valve 4 is open as it is vented to the atmospherethrough the wrench motor. Upon release of the throttle valve 4 thepressure in the conduit 2 and the delivery chamber 19 increases untilthe pressures-on both sides of the piston 11 are again equal. Duringthis increase the piston 11 is urged back to its upper position in thecylinder 9, which position is defined by the stop flange 1d of thehollow member 13 contacting the end wall 9a of the cylinder 9. With thepiston 11 in its upper position the apparatus is ready for the nexttightening cycle. During each cycle equal quantities of live air will bedispensed in the delivery chamber 1% of the device 8 and fed to operatethe wrench 1 as long as the pressure in the supply 7 remainssubstantially constant.

By'rotating the lever 15 to displace the adjustable holloW member 13along the threaded piston stem 12 away from the piston 11 the pistonstroke and consequently the pressure fluid quantity dispensed by thedelivery chamber 19 may be decreased so as to set the device for asmaller number of revolutions of the wrench in case fewer revolutionsprove suificient to give the desired degree of tightness of the bolt ornut. If on the other hand an increase of the dispensed pressure fluidquantity is demanded in order to increase the number of revolutionsperformed by the wrench, such increase may be accomplished by openingand pre-setting the needle valve 24 to a suitable bleed value. Inoperation, as soon as the pressure drop between the chambers 18 and 19is established, an additional live .air quantity is bled from thechamber 18 through the needle valve 24 and the conduit 23 to thedelivery chamber 19 and further to the conduit 2 and the wrench 1.At'the end of the downward stroke the annular sealing pad 21 of thepiston 11 contacts the annular rib 22 of the cylinder 9 and cuts off theadditional'bleed supply to the conduit 2. The piston 11 remains asbefore in this lower position as long as the throttle valve is keptopen. Upon closing of the throttle valve the leakage through thepistonpassage 29 is able to build up the necessary pressure in the conduit 2and inside of the annular rib 22 to initiate the piston return. Onceinitiated the return stroke is effectively accelerated by the live airbleeding through the needle valve 24, which results in a short resettingtime for the next tightening cycle.

With the needle valve 24 opened the piston 11 additionally to its airdelivering action has the function of a timer for controlling theduration of the air flow to the conduit 2 through the conduit 23.

As an alternative the restricted bleed passage 20 may with equalperformance of the device be arranged in the walls or outside of thecylinder 9, directly connecting the conduits it and 2 and by-passing thecylinder chambers 18, 19 as indicated in chain-dotted lines at 29 inFIG. 1. Additionally there may in order to accelerate the piston returnhe provided a further needle valve 24 even in such external bleedbypass, which makes possible a pre setting of the bleed to suit thechanging volumes of the 4t conduit 2 if the device it is to duits 2 ofdifferent lengths.

in the modified embodiment of FIGS. 2 and 3 the needle valve arrangement24 has been omitted While a valve mechanism generally designated 25 andshown in detail in FIG. 3 has been incorporated in the piston 11primarily in order tossecure a rapid return of the piston H to its upperposition.

The valve mechanism 25 incorporates a cylindrical cup shaped valve body25 having bottom perforations 27 and a central projection 28 extendingoutwardly from its bottom. The valve cup 26 is reciprocably arrangedcentrally within a counter bore 29 extending axially through the piston11 from the bottom of a counter bore 2% in the piston. The counter bore2% is covered by a disk having perforations S t-ta therethrough andbeing fixedly secured to the piston for example by screws, not shown.The disk 3% carries centrally a sealing pad 31, which cooperates withthe rim of the valve cup at. A central restricted bleed passage 32extends axially through the disk 3% and the pad 31. A helical spring 34is compressed between the sealing pad 31 and the bottom of the valve cup26 and urges the valve cup 26 into open position away from the sealingpad 31. Normally the spring holds the valve cup 25 pressed against ashoulder 33 in the counter bore 29 in which position the valve mechanism25 is open, there being a communication between the chambers 13 and 19of the cylinder 9 through the perforations Eda of the disk 30, the bore29a, the annular opening between the rim of the valve cup 26 and the pad31 and the perforabe used together with contions 27. In this open valveposition the projection 28 of the valve cup 26 extends into the deliverychamber w of the cylinder 9 In the lower position of the piston Illillustrated in chain dotted lines in FIG. 2, however, the projection 28has been arrested by the cylinder 9, see FIG. 3, to effect closing ofthe valve mechanism 25 with the valve cup rim pressed against the pad31. in this position the piston chambers 18- and 19 communicate solelythrough the restricted passage 32 in the disk 30.

In operation, the piston 11, in analogy with the em bodiment of FIG. 1,feeds the pressure fluid quantity trapped in the delivery chamber 19through the conduit 2 to operate the wrench motor. As the valvemechanism 25 is open during practically the whole downward stroke, anadditional pressure fluid quantity will pass from the pressure chamber18 through the openings defined by the valve mechanism 25 to the chamber19 and further to the conduit 2. Upon reaching the lower or dotted lineposition of FIG. 2 the valve mechanism 25 is closed by the valveprojection 23 contacting the end wall of the cylinder. This stopsfurther tightening of the bolt or nut since the pressure fluid nowdelivered is solely the small quantity bleeding through the passage 32.Upon closing of the throttle valve, however, this small quantity is ableto build up pressure in the conduit 2 as well as in the chamber 19 toinitiate the piston return, which is elficiently accelerated as soon asthe valve mechanism 25 is reopened by the spring 34.

Adjustment of the pressure fluid quantity dispensed is performed bysetting the hollow member 13 axially on the piston stern by turning thelever 15 as previously described with reference to FIG. 1. In order tochange the additional flow of pressure fluid passing through the valvemechanisrnZS, said valve mechanism may be substituted by another valvemechanism having wider or more restricted pressure fluid passagestherethrough.

While in the embodiments of FIGS. 13 as a main feature there isdispensed a predetermined volume of pressure fluid to operate the impactwrench, the modified embodiment of FIG. 4 controls the quantity ofpressure fluid delivered to the wrench by measuring the time elapsedfrom the actuation of the throttle valve of the wrench and by shuttingoff the fluid supply to the impact wrench after apredetermined timecorresponding to a predetermined total fluid delivery.

Referring now to FIG. 4 there is inserted between the conduits it) and 2a solenoid operated shut-oat valve 35 of suitable construction, forexample having a spring pressed plunger 36 keeping a membrane 37 tightlypressed. against the seat of the valve 35. Upon energization of asolenoid 38 the plunger is retracted whereupon the fluid pressure in theconduit is able to force the membrane 3'7 from the seat of the valve 35to open the connection between the conduits it? and 2.

A cylinder 41 forming a servo motor has a piston l2 reciprocablyarranged therein, the rod of the piston 32 projecting through one endwall of said cylinder A conduit 39 connects the conduit it to the pistonrod end compartment 41a of the cylinder ill, while the opposite endcompartment 41b of the cylinder 41 is connected by a conduit it? to theconduit 2. In the conduit ll there is arranged a check valve 44- openingfor flow in the direction towards the conduit 2. Between the endcompartments 41a and @312 of the cylinder 41 there is a bleedconnection, for example attained by an insuificient tightness betweenthe piston 42 and the cylinder 41 or by a separate connecting conduit 45having therein an adjustable needle valve 46. The end compartment ll]?of he cylinder 41 is furthermore connected by a conduit 47 to a solenoidoperated exhaust valve dd, in which for example a spring pressed plunger49 seats a valve pad against the seat or" the valve 48. Uponenergization of a solenoid 5d the plunger 4% together with the valve padis retracted from the seat of the exhaust valve 28 thereby connectingthe end compartment 41b of the cylinder 41 to the atmosphere.

The rod 43 of the piston 42 has lived thereto a lever 5ll which upon thepartial retraction of tL-e rod 43 into the cylinder il depresses theactuating member 52 of a combined timer and switch T. This combinedtimer and switch T may be of conventional design and is therefore notdescribed in detail. It may, for example, be carried out according toGerman Patent Number 937,715 wherein the combined timer and switchincorporates a clockwork mechanism controlled switch, the clockworkbeing pre-settable to variable time values. The functionalcharacteristics of the timer construction selected is preferably suchthat upon depression of the actuating member 52 there is performed asimultaneous closure of the timer switch S3 and starting of theclocitworl; mechanism, whereupon, after elapse of the pre-se time value,the timer opens the switch 53.

Of the two leads 53, 59 from a suitable source 61 of electrical energyone is branched and connected to two double throw switches 54-, 5'6,respectively, of a switch assembly while the other lead 5'9 is connectedto a third double throw switch 55 of said assembly The circuit betweenthe two leads 5%, 59 incorporates in the right hand position in FIG. 4of the switch asse i ly the timer switch 53 and the solenoids 38, 5d,the latter coupled in parallel. In the left hand position of the switchassembly the circuit between the leads solely incorporates the solenoidof the shut-otl valve 35. Suitably connected lamps or other signals 5'7may be coupled to indicate when the respective circuits are completed.

The apparatus according to FIGURE 4- operates briefly in the followingmanner: If the operator with the respective parts in the illustratedposition and with the switch assembly 54456 thrown to the right and thesocket 5 over a nut or bolt 6 depresses the trigger of the throttlevalve 4 then an initial pressure drop will arise in the conduit 2,. Saidpressure drop causes the end compartment lib of the cylinder 5-1 orservo motor to exhaust through the conduit it? and the check valve 44into the conduit 2, some pressure fiuid simultaneously passing from theconduit it through the conduit 39 into the piston compartment lla of thecylinder moving the piston 42 to the right hand end of the cylinder 41.During this movement the lever 51 depresses the actuating member 52 ofthe timer T which closes the switch 53 and starts the clockworkmechanism of the timer. liy closing of the switch 53 the circuit 6between the switches 54-, 525 and 55 of the switch assembly is completedand the solenoids 38 and 59 are energized. This opens the shut-off valve35 to deliver pressure fluid to the impact Wrench 1 and opens theexhaust valve 4-3 to connect t e cnd compartment 41b of the cylinder 41to the atmosphere. A constant bleeding of pressure fluid from theconduit ll) takes place through the conduit 39, the end compartment Allaof cylinder 41, connecting conduit 45, the needle valve 46, the endcompartment dlb of cylinder 41, the conduit 47, and the valve 48 to theatmosphere. This bleeding is set by needle valve as to such small valuethat no pressure can be built up in the end compartment an; of thecylinder 41 which consequently remains in the right hand position. Thecheck valve 44 prevents pressure fluid from the conduit 2 passingthrough the conduit dill to the cylinder il. After elapse of thepredetermined time value at which the timer has been set and whichcorresponds to a sufiicient quantity of pressure fluid delivered throughthe shut-off valve 35 to operate the impact wrench the number ofrevolutions necessary for proper tightening, the timer breaks thecircuit by opening the timer switch 53. Both solenoids 50, 3% are thendeenergized and the respective valves 48, 35 closed which stops theoperation of the impact wrench. The bleeding of pressure fiuid throughthe needle valve 46 continues as long as the throttle valve 4 is keptopen, passing now from the needle valve as through the conduit 4%, thecheck valve 44 and the conduit 2 to the impact wrench. As soon as theoperator releases the throttle valve, the bleeding will rapidly increasethe pressure in the end compartment ll!) of the cylinder 43 until thepiston 42 is returned to its initial left hand position. With thethrottle valve 4 closed and the piston 42 returned, the bleeding comesto an end until the next operating cycle is started.

Obviously, by changing the setting of the timer T, the pressure fluidquantity passing the shut-off valve 35 may be pre-set for different workconditions to bring about the number of revolutions necessary to give adesired degree of tightness in the work.

If the impact wrench is to be used without regard to the resultingtightness, the switch assembly is thrown to the left. This energizessolenoid 33 to keep the valve 35 permanently open for conventional useor the wrench l.

The embodiments of the invention above described and illustrated in thedrawings should only be considered as examples and the invention may bemodified in several different ways within the scope of the followingclaims.

What I claim is:

l. A method for controlling the degree of tightness of a series of boltsor nuts driven by the aid of a pressure fluid operated impact wrenchhaving a throttle valve connected to a fluid supply, comprising applyingthe impact wrench in turn over each bolt or nut to be driven, supplyingpressure fluid to operate the impact wrench when in engagement with eachbolt or nut in response to actuation of the throttle valve, storing apredetermined quantity oi pressure fluid from said fluid supply,dispensing said predetermined quantity of pressure fluid to the impactwrench upon actuation of said throttle valve, and automaticallyinterrupting the wrench operating fluid supply to the impact wrench uponhaving delivered said predetermined quantity for the driving of eachbolt or nut.

2. A method for controlling the degree of tightness of a series of boltsor nuts driven by the aid of a pressure fluid operated impact wrenchhaving a throttle valve connected to a fluid supply, comprising applyingthe impact wrench in turn over each bolt or nut to be driven, supplyingpressure fluid to operate the impact wrench when in engagerent with eachbolt or nut in response to actuation of the throttle valve, storing apredetermined quantity of pressure fluid from said fluid supply,dispensing said predetermined quantity of pressure fluid to the impactwrench upon actuation of said throttle valve and adding thereto acontrolled additional pressure fluid quantity, and automaticallyinterrupting the wrench operating fluid supply 3,1 to the impact wrenchupon having delivered said predetermined quantity and additionalquantity for the driving of each bolt or nut.

3. Apparatus for controlling the degree of tightness of a series ofbolts or nuts driven by an impact wrench comprising a fluid motor fordriving said wrench, a pressure fluid supply, a supply connectionbetween the motor and the fluid supply, a throttle valve in the supplyconnection admitting upon actuation pressure fluid to the motor, presure fluid dispensing means in the supply connection for delivering acontrolled volume of pressure fluid to operate the motor in response toactuation of the throttle valve, and bleed means in parallel with thedispensing means for adding a controlled additional quantity of pressurefluid to said controlled volume, the dispensing means interrupting thewrench operating fluid supply to the motor upon the motor havingreceived said controlled volume and additional quantity. t. Apparatusfor controlling the degree of tightness of a series ofbolts or nutsdriven by an impact wrench comprising a fluid motor for driving saidwrench, a pressure fluid supply, a supply connection between the motorand the fluid supply, a throttle valve in the supply connectionadmitting upon actuation pressure fluid to the motor, a dispensingcylinder in the supply connection, differential piston means dividingthe cylinder into a piston stem end compartment and a dispensirncompartment and deliver ing the fluid volume contained in the dispensingcompartment to operate the motor in response to actuation of thethrottle valve, an inlet on the cylinder for connecting the piston stemend compartment to the fluid supply, an outlet on the cylinder forconnecting the dispensing compartment to the motor, a permanent bleedconnection between said inlet and said outlet, an additional bleedconnection between said compartments, and means for closing saidadditional bleed connection upon the piston having delivered the volumecontained in the dispensing compartment to the motor. I

5. Apparatus according to claim 4, in which the additional bleedconnection is arranged in the cylinder and said means for closing theadditional bleed connection consists of a valve seat surrounding theoutlet and sealing means on the piston cooperating with the seat.

' 6. Apparatus according to claim 4, in which the additional bleedconnection is arranged in the piston and consists of a bleed valve, themeans for closing said valve consisting of a projection on the valvecontacting the cylinder when closing the valve.

7. In apparatus for controlling the maximum torque applied to each nutor bolt in driving a series of nuts or bolts and including an impactwrench with a fluid motor and a source of pressure fluid therefor, thecombination which comprises a supply connection between said motor andsaid source of pressure fluid, a throttle valve in said supplyconnection, storage and delivery means in said supply connection forstoring a predetermined quantity of pressure fluid from said source anddelivering said predetermined quantity of pressure fluid to said motorupon actuation of said throttle valve, said storage and delivery meansautomatically interrupting said supply of pressure fluid to said motorupon delivery or" said predetermined quantity of pressure fluid, andbleed-means in said storage and delivery means for resetting saidstorage and delivery means for the next application of said impactwrench upon closing of said throttle valve.

8. In apparatus for controlling the maximum torque applied to each nutor bolt in driving a series of nuts or bolts and including an impactwrench with a fluid motor and a source of pressure fluid therefor, thecombi nation which comprises a supply connection between said motor andsaid source of pressure fluid, a throttle valve in said supplyconnection, storage means in said supply connection for storing apredetermined quantity of pressure fluid from said source, a moveablefeeding member in said storage means for delivering said predeterminedquantity of pressure fluid to said motor upon actuation of said throttlevalve, said feeding member automatically interrupting said supply ofpressure fluid to said motor upon delivery of said predeterminedquantity of pressure fluid, and bleed means in said feeding member forresetting said storage means and feeding member for the next applicationof said impact wrench upon closing of said throttle valve. r

9. Apparatus as recited in claim 8 which also includes means connectedto said feeding member for adjusting the predetermined quantity ofpressure fluid to be stored in said storage means.

it). In apparatus for controlling the maximum torque applied to each nutor bolt in driving a series of nuts or bolts and including an impactwrench with a fluid motor and a source of pressure fluid therefor, thecombination which com rises a supply connection between said motor andsaid source of pressure fluid, a throttle valve in said supplyconnection, storage means in said supply'connection for storing apredetermined quanity of pressure fluid from said source of pressurefluid, a feeding memher in said storage means for delivering saidpredetermined quantity of pressure fluid to said motor upon actuation ofsaid throttle valve, said feeding member automatically interrupting saidsupply of pressure fluid to said motor upon delivery of saidpredetermined quantity of pressure fluid, bleed means parallel with saidfeeding member for resetting said storage means and feeding member forthe next application of said impact wrench upon closing of said throttlevalve, and second bleed means from said pressure fluid source to saidmotor and by-passi'ng around said storage means and feeding member forsupplying an additional predetermined quantity of pressure fluid fromsaid pressure fluid source to said motor, said feeding member alsoautomatically interrupting said second bleed means supply to said motorupon delivery of said stored predetermined quantity of pressure fluid.

11. In apparatus for controlling the maximum torque applied to each nutor bolt in driving a series of nuts or bolts and including an impactwrench with a fluid motor and a source of pressure fluid therefor, thecombination which comprises a supply connection between said motor andsaid source of pressure fluid, a throttle valve in said supplyconnection, metering means in said supply connection for metering anddelivering a predetermined quantity of pressure fluid to said motor fromsaid pressure fluid source upon actuation of said throttle valve and forinterrupting the flow of pressure fluid from said source to said motorupon delivery of said predetermined quantity of pressure fluid, andbleed means from said pressure fluid source to said motor and parallelwith said metering means for supplying an additional predeterminedquantity of pressure fluid from said pressure fluid source to said motorand connected to said metering means for the resetting thereof for thenext application of said impact wrench upon closing of said throttlevalve.

12. in apparatus for controlling the maximum torque applied to each nutor bolt in driving a series of nuts or bolts and including an impactwrench with a fluid motor and a source of pressure fluid, thecombination which comprises a supply connection between said motor andsaid source of pressure fluid, a throttle valve in said supplyconnection, supply valve means in said supply connection, meansconnected to said supply valve means and responsive to said throttle foropening said supply valve means upon actuation of said throttle fordelivering a predetermined quantity of pressure fluid to said motor andfor automatically closing said supply valve means upon delivery of saidpredetermined quantity of pressure fluid, and bleed means from saidpressure fluid source to said motor and parallel with said supply valvemeans for supplying an additional predetermined quantity of pressurefluid from said pressure fluid source to said motor and connected tosaid supply valve means for the resetting thereof for the nextapplication of said impact Wrench upon closing of said throttle valve.

13. A method or" controlling the degree of tightness of a series ofbolts or nuts driven by the aid of a pressure fluid operated impactwrench having a throttle valve connected to a fluid supply, comprisingtaking from said supply for each bolt or nut to be driven apredetermined volume of pressure fluid, storing each said predeterminedvolume of pressure fluid, applying said impact wrench in turn over eachbolt or nut to be driven, and supplying each said stored predeterminedfluid volume to said impact wrench when in engagement with each bolt ornut in response to actuation of said throttle valve.

14. A method of controlling the degree of tightness of a series of boltsor nuts driven by the aid of a pressure fluid operated impact wrenchhaving a throttle valve connected to a fluid supply, comprising takingfrom said supply for each bolt or nut to be driven a predeterminedvolume of pressure fluid, storing each said predetermined volume ofpressure fluid, applying said impact wrench in turn over each bolt ornut to be driven, supplying each said stored predetermined fluid volumeto said impact Wrench when in engagement with each bolt or nut inresponse to actuation of said throttle valve, and passing a controlledadditional flow of pressure fluid from said supply to said throttlevalve while supplying said stored fluid volume.

15. Apparatus for controlling the degree of tightness of a series ofbolts or nuts driven by an impact Wrench comprising a fluid motor fordriving said wrench, a pressure fluid supply, a supply connectionbetween said motor and said fluid supply, a throttle valve in saidsupply connection for admitting upon actuation pressure fluid to saidmotor, collapsible chamber means in said supply connection upstream ofsaid throttle valve, means responsive to closing of said throttle valvefor expanding and filling said collapsible chamber means by pressurefluid received from said supply thereby to store a predetermined volumeof pressure fluid therein, and means responsive to opening of saidthrottle valve for collapsing said collapsible chamber means and fordelivering said predetermined volume of pressure fluid contained thereinto operate said motor.

16. Apparatus according to claim 15 in which the volume of saidcollapsible chamber means in the expanded state thereof is adjustable.

1'7. Apparatus for controlling the degree of tightness of a series ofbolts or nuts driven by an impact wrench comprising a fluid motor fordriving said Wrench, a pressure fluid supply, a supply connectionbetween said motor and said fluid supply, a throttle valve in saidsupply connection for admitting upon actuation pressure fluid to saidmotor, collapsible chamber means in said supply connection upstream ofsaid throttle valve, first bleed means between said supply and saidthrottle valve responsive to closing of said throttle valve forexpanding and filling said collapsible chamber means by pressure fluidreceived from said supply thereby to store a predetermined volume ofpressure fluid therein, means responsive to opening of said throttlevalve for collapsing said collapsible chamber means and for deliveringthe predetermined volume of pressure fluid contained therein to operatesaid motor, second bleed means between said supply and said collapsiblechamber means, and valve means associated with said collapsible chambermeans and responsive to collapse thereof for closing said second bleedmeans.

References Cited by the Examiner UNITED STATES PATENTS 1,589,080 6/26Kyle. 2,365,537 12/44 Fisher et a1 81-5235 2,664,106 12/53 Livers.2,820,566 1/58 Van Hecke 121-3 2,825,353 3/58 Voytech 121-35 2,830,5605/58 Doeden 121-34 2,852,965 9/5 8 Wallace.

3,005,444 10/61 Steibel 121-38 3,033,236 5/62 Rayman et al. 121-33FOREIGN PATENTS 741,344 11/55 Great Britain.

BROUGHT ON G. DURHAM, Primary Examiner.

KARL I. ALBRECHT, RALPH H. BRAUNER,

Examiners.

1. A METHOD FOR CONTROLLING THE DEGREE OF TIGHTNESS OF A SERIES OF BOLTSOR NUTS DRIVEN BY THE AID OF A PRESSURE FLUID OPERATED IMPACT WRENCHHAVING A THROTTLE VALVE CONNECTED TO A FLUID SUPPLY, COMPRISING APPLYINGTHE IMPACT WRENCH IN TURN OVE EACH BOLT OR NUT TO BE DRIVEN, SUPPLYINGPRESSURE FLUID TO OPERATE THE IMPACT WRENCH WHEN IN ENGAGEMENT WITH EACHBOLT OR NUT IN RESPONSE TO ACTUATION OF THE THROTTLE VALVE, STORING APREDETERMINED QUANTITY OF PRESSURE FLUID FROM SAID FLUID SUPPLY,DISPENDING SAID PREDETERMINED QUANTITY OF PRESSURE FLUID TO THE IMPACTWRENCH UPON ACTUATION OF SAID THROTTLE VALVE, AND AUTOMATICALLYINTERRUPTING THE WRENCH OPERATING FLUID SUPPLY TO THE IMPACT WRENCH UPONHAVING DELIVERED SAID PREDETERMINED QUANTITY FOR THE DRIVING OF EACHBOLT OR NUT.